He hasn't been allowed so much as a bathroom break. Because of Senate rules, he cannot leave the Senate floor, cannot sit down, and can only yield briefly to his colleagues for "questions." He has only had a few bites to eat.

But the question you're probably asking is this:

How has Cruz managed to go 20 hours without even a bathroom break?

In Cruz's situation, this is unclear. A Cruz spokesperson didn't immediately respond to an email seeking clarification. But he has not left the floor, or he would cede control of the floor and not be able to continue speaking.

There are different precedents for bathroom breaks during filibusters. (Technically, under Senate rules, Cruz's talk-a-thon isn't a "filibuster," because he is not blocking or delaying a vote on a legislation.)

Thurmond, who still holds the record for the longest filibuster in Senate history, went for more than 24 hours to block civil-rights legislation. How did he do it? According to NPR, he "aides tried to avoid defeat by the toilet by setting up a bucket in the cloakroom where Thurmond could pee, keeping one foot on the Senate floor while doing so."